Geochemistry

Weathering

Metallurgy

Materials science

Earth science

Geology

Soil water

Environmental science

Soil science

Rare earth

Tailings

Leaching (pedology)

Nature Sustainability

Heavy rare earth elements (HREEs) such as Gd–Lu, Sc and Y are irreplaceable metals for a number of critical (including clean) technologies, but they are scarce. Ion-adsorption deposits, which form within weathering crusts, supply more than 95% of the global HREE demand. However, these deposits are currently mined via ammonium-salt-based leaching techniques that are responsible for severe environmental damage and show low recovery efficiency. As a result, the adoption of such techniques is restricted for REE mining, further exacerbating REE scarcity, which in turn could lead to supply chain disruptions. Here we report the design of an innovative REE mining technique, electrokinetic mining (EKM), which enables green, efficient and selective recovery of REEs from weathering crusts. Its feasibility is demonstrated via bench-scale, scaled-up and on-site field experiments. Compared with conventional techniques, EKM achieves ~2.6 times higher recovery efficiency, an ~80% decrease in leaching agent usage and a ~70% reduction in metallic impurities in the obtained REEs. As an additional benefit, the results point to an autonomous purification mechanism for REE enrichment, wherein the separation process is based on the mobility and reactivity diversity between REEs and metallic impurities. Overall, the evidence presented suggests that EKM is a viable mining technique, revealing new paths for the sustainable harvesting of natural resources. Heavy rare earth elements are critical for modern technological applications, including renewable energy technologies, but their extraction can have disastrous environmental impacts. Employing electrokinetic mining techniques can increase recovery efficiency while reducing harmful environmental consequences.

A green and efficient technology to recover rare earth elements from weathering crusts